PHYLOGENETIC ADAPTATION OF THE PIGMENT SYSTEM 



423 



Table 15.VIII 

 Influence of the "Light Field" on Pigments in Green Plants 



It was mentioned on page 405 that the systematic investigation of 

 marine algae has revealed the limitation of the conception of the ratio of 

 [a]:[b] as an expression of chromatic adaptation. Instead of very 

 large relative concentrations of chlorophyll b, almost all deep-sea algae 

 were found to contain no chlorophyll b whatsoever. However, from the 

 point of view of light absorption, the deficiency of chlorophyll b in brown 

 algae is compensated for by the presence of fucoxanthol. 



Seybold and Egle (19380 found that chlorophyll a is produced in 

 light more rapidly than chlorophyll b, so that the ratio of [a] : [b] can 

 attain very large values in the first period of illumination of etiolated 

 seedlings. The same factor may perhaps account for the larger stationary 

 concentration of chlorophyll a in sun-exposed leaves. Willstatter and 

 Stoll (1918) found, however, (as mentioned before) no indication of an 

 increase in the ratio of [a]: [b] after 10-20 hours of intense illumination. 



The effect of environment on the concentration of the carotenoids 

 and on the ratio of [chlorophyll]: [carotenoids] also has been probed by 

 Rudolph (1934), Seybold and Egle (1937, 1938i'2), Simonis (1938), and 

 Strott (1938). Seybold and Egle (1937) thought at first that "shade 

 plants" contain relatively more carotenoids. Later (1938"), they found 

 (cf. Table 15.VIII) that the ratio of ([a] -t- [b]:[x] -f [c]) is not 

 affected systematically by the intensity of illumination; but that the 

 ratio of [x] : [c] is larger in shade plants, although less consistently so 

 than that of [a]:[b]. Thus, the relative concentrations of the "oxi- 

 dized" pigments (chlorophyll b and the carotenols) are lower in plants 

 adapted to strong light. The different composition of the carotenoid 

 mixture in shade plants and sun plants can hardly be attributed to 

 chromatic adaptation, since the substitution of luteol for carotene does 

 not increase the efficiency of light absorption. 



Recently, Seybold (1941) suggested that chlorophyll b is associated 



with starch production, and absent from plants which form only soluble 



- sugars. The basis of this theory was the observation that Vaucheria, 



